CargoCap – Speed-Sensorless Induction Motor Drive System for Underground Pipeline Capsule Transportation

Andreas Steimel, Ruhr-University Bochum, Germany

Marcus Grimmig, Ruhr-University Bochum, Germany

At Ruhr-University Bochum an innovative concept of transportation of mixed cargo through subterranean pipelines with driverless, automatically and individually controlled capsules - CargoCap - is under development. From the mechanical specifications as masses, speed, acceleration and resistance the tractive/braking effort vs. speed diagram is deduced which serves as basis for the layout of the electrical drive.

For maximum reliability four squirrel-cage induction motors fed by two voltage-source IGBT inverters have been selected as main drive, representing the state-of-the-art of Light Rail vehicle drives.

For the control of the variable voltage variable frequency (VVVF) inverter the so-called Indirect Stator-Quantities Control based on stator-flux orientation is presented, which attains high torque dynamics as well as it is extremely robust against supply voltage disturbations.

From the aspects of cost, reliability and drive volume it is recommended to dispense with speed sensors in the motors. A new scheme to estimate the speed with high accuracy only from motor quantities already available in the control is described. It enables speed estimation even in the case of infinitely slow changes between driving and braking at extremely low speeds.